TY - JOUR T1 - THE EFFECT OF CALCIUM AND POTASSIUM ON CARDIAC REACTIONS TO MERCURY JF - Journal of Pharmacology and Experimental Therapeutics JO - J Pharmacol Exp Ther SP - 407 LP - 421 VL - 41 IS - 4 AU - WILLIAM SALANT AU - HAROLD NAGLER Y1 - 1931/04/01 UR - http://jpet.aspetjournals.org/content/41/4/407.abstract N2 - 1. In concentrations above 1:500,000, mercury in normal Ringer decreased the force as well as the frequency of the contractions, and heart action often became irregular. Slowing was more frequently obtained with low concentrations and was abolished by atropine. The resistance was greatly decreased in the hypodynamic heart also by interrupted treatment with mercury. 2. Mercury in Ringer's solution with reduced amounts of calcium produced marked stimulation, but depression also occurred in some cases, particularly with medium concentrations of mercury. This reversal of action was probably caused by changes in the buffer and by the presence of volatile toxic substances in Ringer's solution. 3. Mercury in Ringer solution containing increased amounts of potassium also produced cardiac stimulation. When potassium was removed from the solution, mercury produced cardiac irregularity, but this was followed in most experiments by improved heart action, although the amplitude was smaller than in the control period. 4. Excess calcium sometimes greatly retarded the action of mercury, thus reducing the toxicity considerably. 5. The effect of high concentrations of mercury in normal Ringer is the same as when this contains increased amounts of calcium. 6. The effects of potassium and calcium on the response of the heart to mercury were discussed. 7. It was suggested that stimulation by mercury when calcium was low, or potassium was increased, was probably due primarily to excitation of the pace-maker by mercury and stimulation of the auricles by increased potassium-calcium ratio, the ventricle being secondarily stimulated by the increased volume of fluid from the auricles, and also by the increased flow of impulses from the sinus and auricles. 8. The decreased toxicity of mercury caused by excess calcium was explained by diminished permeability believed to be produced by calcium, and also by the stimulation which this produces in the ventricle. It was also pointed out that calcium protected the heart against poisons other than mercury and that potassium and mercury often showed syngerism. ER -